Reduce joist height

[burts]

Morning, I have just built a second storey extension on top of a ground floor extension (which was done 3 years ago).
I’ve knocked through in to the existing bedroom and the new floor is 20mm higher than the existing. I don’t want it ramped, feathered or existing raised creating a step at the door bar.
So my question is, what is the best way to take 20mm of the joists and noggins on the new extension floor?

 

[freddiemercurystwin]

Will your joists still be of an adequate depth if you embark upon this madness?

 

[burts]

Will your joists still be of an adequate depth if you embark upon this madness?

1. Yes I know it’s madness but it’s really going to pi** me off and 2. Yes there is plenty of joist depth.
What would you do with it?
20mm is to much to lose in my opinion as the original room is only small, less than 2m and the floor is already un level and not in my favour

 

[robinbanks]

How are the joists supported? Pictures would help. Notching the bearing surface rather than the joist would be better, structurally

Yes there is plenty of joist depth.

How do you know?

and the floor is already un level

Er, so you have somehow been able to forgive that all these years but 20mm feathered out is going to drive you mad?

Why not level everything right through then none of it annoys you?

 

[burts]

How are the joists supported? Pictures would help. Notching the bearing surface rather than the joist would be better, structurally


How do you know?


Er, so you have somehow been able to forgive that all these years but 20mm feathered out is going to drive you mad?

Why not level everything right through then none of it annoys you?

The house was built in 2008.
I moved in and built a rear extension. The joists in the rear extension were sized to accommodate a second storey in the future which is what I’ve now done. The joists new joists were 245mm by 45mm (nearest match to the original house to try achieve same level, existing house joists are two pieces of 2x2 with osb between which I’ve never seen before) So I know the new joists are more than enough.

When I’m talking about the level on the floor, it hasn’t annoyed me at all but what I’m saying is it’s already running out so feathering it out will be making it worse and if it’s starts running out now by 40mm from the middle of the room to the door then it will notice especially on the skirtings.

I could level the floor with 18mm osb on the existing but I don’t want an 18mm lip between the room and the hallway because every room runs through flush

 

[foxhole]

Morning, I have just built a second storey extension on top of a ground floor extension (which was done 3 years ago).
I’ve knocked through in to the existing bedroom and the new floor is 20mm higher than the existing. I don’t want it ramped, feathered or existing raised creating a step at the door bar.
So my question is, what is the best way to take 20mm of the joists and noggins on the new extension floor?

Why did you not install the joist to the correct height in the first place?

 

[burts]

Why did you not install the joist to the correct height in the first place?

Why do you think that response helps me in any way? Why do people come on here to moan rather than try to help.
What do you think the obvious reason is? Because the ground floor was built 3 years prior and I wasn’t going to knock through my house.

 

[StephenStephen]

Can you move the new joists downwards?

 

[freddiemercurystwin]

There's no need to get defensive, it's a perfectly reasonable question, it also begs the question why didn't you use joists of the right size rather than apparently over-specifying them?

Anyway I guess it would be a combination of different saws, circular, hand, multisaw and a plane.

BTW the existing house joists are nothing new, they're just called engineered I joists.

 

[Murdochcat]

Dare I suggest you ask your BCO?

 

[burts]

Can you move the new joists downwards?

No. It’s my living room. It’s been completed for 3 years

 

[burts]

There's no need to get defensive, it's a perfectly reasonable question, it also begs the question why didn't you use joists of the right size rather than apparently over-specifying them?

Anyway I guess it would be a combination of different saws, circular, hand, multisaw and a plane.

BTW the existing house joists are nothing new, they're just called engineered I joists.

I appreciate I shouldn’t get defensive but it’s hard when you’re already stressed and it’s clear I was never going to get it bang on without doing both at the same time and knocking through 3 years ago.
The engineered joists in the original house are 240mm which I measured through a spot light when doing downstairs so I used the nearest size joist to match the height. So i didn’t over specify for any reason other than match the height I needed which juts so happened to be more than what building control required.
When my bricklayer has done the downstairs extension the internal skin is 15-20mm higher than the existing house, but it would have been impossible for him to get that perfect, all he’s done is aligned the external skins.

 

[cdbe]

You can batten the sides of the joists and drop the flooring in.

 

[burts]

You can batten the sides of the joists and drop the flooring in.

I did think of this but then the floor is only as strong as the battens? Not sure that is structurally ok. ?

 

[SFK]

Never done this but...

I would not do it as I would be worried for evermore about compromising joist strength.

But if I did I would used a router.
Make up a jig so it only takes out middle section off the top of the joist.
So you have a wide as possible U section cut out of joist.
The jig would be so you Leave say 4mm on each side.
This is to keep router on a flat plane.
Then take out the side 4mm bits with a chisel.
You alo need a great vacuum as there will be a lot of chippings.
Sfk